The present invention relates to a washing machine of the vertical-axis type of the washing of fabric articles such as clothes, and more particularly to washing machines that have a system for detecting and correcting an out-of-balance condition during the spin cycle.
Automatic clothes washing machines customarily provide a sequence of operations in order to wash, rinse, and extract water from the clothes contained in a basket. A typical type clothes washing machine is shown and described in U.S. Pat. No. 3,570,274 assigned to the same assignee as the present invention. Such clothes washing machines have a non-rotating outer water containing tub and an inner perforated basket, the latter of which, during centrifugal liquid extraction operations, is spun at high speed so that liquid is forced from the clothes within the basket through the perforations in the basket and into the outer tub. From the outer tub the liquid is removed from the machine to a drain by an conventional pumping means. The sequence of operations ordinarily includes a washing operation which, in one typical of vertical axis machine, is provided by an agitator movably arranged to oscillate back and forth within the basket; a first centrifugal liquid extraction operation in which the wash water is removed from the clothes by spinning the basket; a rinsing operation in which the clothes in the basket are rinsed in clean water while the agitator is oscillated; and a final centrifugal liquid extraction operation in which the basket is spun to remove the rinse water from the clothes. Machines having this type of cycle, or a variation thereof, generally produce highly satisfactory results in that the clothes in the machine come out properly cleaned and with a substantial part of the liquid removed.
One disadvantage that can occur in such a clothes washing machine during the centrifugal liquid extraction operations or spin mode is that should the articles being washed bunch up or have unequal weight distribution about the axis of rotation the basket may become unbalanced. If the unbalance is sufficient during acceleration of the spinning basket, the basket may strike the outer tub which can result in injury to the machine and in some cases the striking may be so violent that the basket is prevented from reaching its intended rotational speed. The unbalance capacity of a given clothes washer machine is most noticeable when the clothes basket is being accelerated through its critical or resonance of vibration speed where it is likely to strike the tub due to an unbalance within the basket. It has been known that if the mass of the basket is increased such as for example by retaining a relatively high volume of water within the basket during its acceleration through the critical speed that the unbalance capacity will be improved. Accordingly unbalance problems most likely occur with small wash loads rather than large loads. For instance, such prior art disclosures are found in U.S. Pat. Nos. 3,306,082 and 2,976,998. The problem with these prior art clothes washing machines, however, is that while a greater volume of water may aid in improving the unbalance capacity of a machine, it detrimentally affects the power consumption necessary to accelerate the basket. In many cases the motor is insufficient to handle the load without increasing its size. In addition, the capability of extracting liquid from the clothes during the spinning is sacrificed.
The out-of-balance problem during the spin mode of a clothes washing operation is also present in orbital type washing machines such as, for example, the machine disclosed in U.S. patent application, Ser. No. 142,949, by John Bochan, filed Apr. 23, 1980. The orbital type washing machine is a vertical-axis type having a dynamic system which includes a single perforate wash basket arranged to be driven continuously such that its central axis moves in an orbital path about another axis. The basket is restrained from rotating about its central axis when it is moving about the other axis and each point of the basket moves in a circulate path having an effective diameter which is small in relation to the diameter of the basket and having substantially the same excursion as the orbital path of the central axis of the basket. Water and soil removing agents are introduced into the basket during orbital motion and that motion is effective to induce a continuous motion of the fabric article load for washing the load. Following washing preferably, the basket's central axis is positioned in substantial alignment with the axis about which it was orbiting and is rotated about this axis to centrifugally remove water from the fabric load. In order to achieve a satisfactory clothes washing operation and to avoid excessive loading of the motor, a means for automatically detecting and correcting any out-of-balance condition during the spin mode is desirable.
It is therefor an object of the present invention to provide a vertical-axis washing machine with means for detecting an out-of-balance condition during the spin mode early in the spin cycle and means for interrupting the spin mode upon detection of an out-of-balance condition and initiating a rebalance cycle and thereafter resume the spin mode.